1. Field of the Invention
Embodiments of the present invention relate, at least as discussed herein, to an hard disk drive apparatus, medium, and method, and more particularly, to an apparatus, medium, and method performing a seek mode, e.g., in a hard disk drive, at an optimum state with respect to an operational temperature.
2. Description of the Related Art
Generally, hard disk drives are one of several data storage apparatuses that reproduce data recorded on a medium, such as a disk, and/or that write user data on such a medium using a magnetic head, for example, and by doing so, may play a contributory role in operating a computer system, for example.
Recently, disk drives have been widely used in a variety of fields such as consumer electronic products, vehicle navigation apparatuses, etc., in addition to such computer systems. Accordingly, the available environments in which disk drives may operate, especially with regard to temperature conditions, have become more diversified.
Also, as disk drives are increasing in capacity and density, as well as decreasing in size, there has been an increase in bits per inch (BPI), i.e., the density in the disk rotation direction, and tracks per inch (TPI), i.e., the density along the radius direction. Accordingly, with such increases there is a need for a more precise control mechanism.
A disk drive may have a plurality of magnetic transducers capable of writing information on and/or reading information from a single, or plurality, of disks, e.g., by sensing and magnetizing magnetic fields along portions of each of the disks. This information may be stored in a plurality of sectors in circular tracks, for example, with track numbers being given to tracks disposed on each surface of the disks. The number of tracks being vertically similar may sometimes be referred together as a cylinder, and accordingly, a singular track may sometimes be defined by its corresponding cylinder number.
Typically, each transducer may be integrated along the inside of a slider attached to a head gimbal assembly (HGA), with each HGA being attached to an actuator arm, for example. The actuator arm may have a voice coil located close with a magnetic assembly defining a voice coil motor. Accordingly, such a hard disk drive may typically include a corresponding driving circuit and controller providing a current exciting the voice coil motor. The excited voice coil motor may, thus, rotate the actuator arm such that transducers move across the surface of the disk(s) for reading and/or writing data from/to a corresponding disk.
When information is written and/or read, the hard disk drive may perform a seek routine to move the transducer from one cylinder to another. During this seek routine, the voice coil motor may be excited by a current so as to move transducers to a cylinder position over the surface of the disk. The controller may perform a servo routine, e.g., for guaranteeing that the transducer moves to a target cylinder and, potentially, a center portion of a track accurately.
It is typically desirable that the amount of time required for reading information from and/or writing information to disk(s) is minimized. Accordingly, the seek routine performed by the drive should move transducers to a new cylinder position within the shortest amount time. Additionally, the settling time of the HGA should typically be minimized in order for the transducer to write an/or read information quickly and to be positioned close to a new cylinder. That is, a seek time, which may be a measure of hard disk drive's performance evaluation, should be minimized.
In a seek mode, acceleration, velocity, and position trajectories in relation to a seek length may be generated, and error values between a current velocity and current position and a design, e.g., ideal or expected, velocity and design position generated based on the acceleration trajectory may be fed back. Then, a corresponding seek current may be applied to the voice coil motor. This design trajectory may be derived from modeling of the voice coil motor and the driving circuit, for example.
This design trajectory may be designed based on an idealistic model, for example, with the difference of the model and an actual system being designed to have sufficient margins so to avoid potential variance problems. As another example, a representative technology, as discussed in U.S. Pat. No. 6,801,384, is to use a seek servo algorithm of an idealistic sine waveform designed with consideration of a power supply constraint.
Generally, if the environmental operational temperature of a hard disk changes, the performance of the disk drive also changes. For example, as the temperature rises, the resistance value of the coil in the voice coil motor increases, and by diminution of magnetic force of the permanent magnet, a corresponding torque constant decreases such that the seek trajectory designed based on an idealistic environment cannot be followed in a high temperature, or if it is followed the result is unacceptable. Accordingly, the seek trajectory has been designed based on worst case high temperature, which in turn causes degradation of the seek performance at room temperatures.